A conventional ignition timing control device for an internal combustion engine retards the ignition timing when acceleration of an internal combustion engine is detected and then controls the ignition timing when the change in the rotational speed of the internal combustion engine reaches a positive value such that the torque will have a phase opposite to that of the acceleration vibration phase in order to prevent an acceleration shock (see Japanese Patent Application Publication No. 5-321803 (JP-A-5-321803)).
The change in torque of an internal combustion engine per unit time when accelerating (which may be hereinafter referred to as “torque gradient”) has a large effect on shock, which occurs during acceleration (which may be hereinafter referred to as “acceleration shock”), or the acceleration performance. The above device causes the torque to have a phase opposite to the acceleration vibration phase during acceleration to prevent an acceleration shock. However, the device does not control the torque based on the torque gradient during acceleration and thus may excessively decrease the torque. In this case, the torque increases slowly during acceleration and the increase in torque is gentle, resulting in low acceleration performance.